A survey released this week by Harvard University’s Institute of Politics found that about two-thirds of likely young voters said their preference is for the midterms to produce a Democratic-controlled Congress, while 32 percent said they want the outcome to be a Republican-controlled Congress. Trump’s approval rating among likely young voters was 25 percent.

The survey found that 40 percent of 18- to 29-year-olds said they will definitely vote in the upcoming congressional elections. According to U.S. census data cited by the Harvard researchers, the last midterm elections in which young voter turnout exceeded 20 percent were in 1994 and 1986.

Peter Levine, an associate dean at Tufts University who oversees the school’s Center for Information and Research on Civic Learning and Engagement (CIRCLE), said it’s clear that young voters could be difference-makers — if they show up.

“They can make a huge difference to the outcome because they’re quite numerous, they’re indicating that they’re going to vote at a much higher rate than they have in past midterms, and they tend to vote differently from older people,” he said.

“Part of our strategy is appealing to people who are younger and who want change,” Scholten told The Hill after the rally at Iowa State.

The race between Scholten, who at 38 describes himself as the “oldest millennial,” and King, 69, appears to be an increasing concern for Republicans, since King has drawn negative attention recently for associating himself with far-right politicians and groups in other countries.

The state is home to a number of colleges, and three of the state’s four congressional districts have competitive races.

Iowa’s 1st Congressional District, held by GOP Rep. Rod Blum, includes 20 different colleges. His Democratic challenger, Abby Finkenauer, is 29 and often talks about still having student-loan debt. CIRCLE said in the spring that the district was the top House race where young voters could decide the outcome.

“It matters to us the most because we will be here the longest to vote,” said Olivia Habinck, president of the Des Moines Area Community College Democrats and the College and Young Democrats of Iowa.

The Democratic Congressional Campaign Committee (DCCC) this election cycle is spending almost $30 million on efforts to target members of the party’s base, including millennials, women and minorities. The efforts to boost turnout among millennial voters has included voter-registration programs and early vote events on college campuses, text messages to millennial voters and digital ads.

“We have built an unprecedented grass-roots operation at the DCCC and a huge focus of that program has been directed on engaging and turning out younger voters,” said DCCC spokesman Tyler Law.

Outside groups are also pushing to boost young adult turnout in an effort to help Democrats. NextGen America, a group founded by Democratic mega-donor Tom Steyer, has representatives organizing in 11 states on more than 400 college campuses, including about 135 community college campuses.

“The enthusiasm and energy from young voters we’ve seen this year is really special and different,” said NextGen America spokesman Will Simons, which cited inspiration from the Parkland, Fla., students who became prominent gun control activists following a mass shooting at their high school.

Republicans are engaging in their own outreach to young voters and hope to limit Democrats’ advantage. The Harvard poll found a 7-point increase from April in the percentage of young Republicans who said they are likely to vote.

Several days after Sanders and Scholten held a rally on Iowa State’s campus, the school’s College Republicans held a meet-and-greet event that featured King.

“We have a great group of conservatives at Iowa State who are pro-life and pro-2nd Amendment and just want the government to let them take care of themselves,” Jeff King, Steve King’s son and campaign chairman, said in an email to The Hill. “It was a really good event they put on.”

Groups such as the Young Republican National Federation and College Republican National Committee have been working to boost voter turnout among younger Republicans as well as those in the party of other ages.

Young Republican Chairman Jason Emert said that while metrics show that young people skew Democratic, “we have a lot of energized members in our organizations.”

The Republican National Committee (RNC) has a fellowship program for high school students as well as another fellowship program that’s largely participated in by millennials. The group also launched a campus team leader program for college students in the spring that trains student organizers who can help to excite young GOP voters ahead of the midterms.

“This is the RNC’s most expansive, well-funded and acutely targeted youth engagement program to date, and it’s allowed for us to have a significant presence in high schools, on college campuses and all across the country,” said Mitch Freckleton, national director of youth engagement for the RNC. “It’s this combination of factors that’s allowed us to identify, engage and turnout young conservative supporters and why I know that we’ll give Democrats a run for their money with youth vote turnout come November 6th.”